Seasonal variations of cave dripwater hydrogeochemical parameters and δ13CDIC in the subtropical monsoon region and links to regional hydroclimate

Stalagmites are considered natural archives of climate proxies. However, under the combined effects of atmospheric circulation patterns, precipitation, and karst environments, drip hydrogeochemical processes can be coupled and linked to each other to control cave sediment record information. Therefore, the evolution of chemistry and factors controlling the isotopic composition of the dripwater during regional precipitation migration from the surface to caves need to be evaluated. In this study, hydrogeochemical characteristics and the isotopic composition of the dripwater in the Mahuang Cave in Guizhou Province, Southwest China, including stable isotope (delta C-13(DIC)) and trace element ratios, were monitored from August 2018 to December 2020. The results showed seasonal variations in the delta C-13(DIC), Mg/Ca, and Sr/Ca values of the dripwater in dry and wet seasons under the control of water-gas-rock reactions, such as soil CO2 concentrations and carbonate rock dissolution. In addition, the five monitored dripwater points in the Mahuang Cave showed fast and slow seepage due to the complex cave fractures and stratigraphy, reflecting the effects of precipitation variations to different degrees. Indeed, the delta C-13(DIC) were more sensitive to the recharge changes from extreme precipitation and drought events. Therefore, dripwater delta C-13(DIC) is a reliable indicator of the recorded hydrological signal in the southwest monsoon region.

Automated summary

By studying the hydrogeochemical characteristics and isotopic composition of dripwater in a cave in southwest China, it was found that the δC-13(DIC), Mg/Ca, and Sr/Ca values of the dripwater showed significant seasonal variations, indicating the influence of water-gas-rock reactions such as soil CO2 concentrations and carbonate rock dissolution. The fast and slow seepage of dripwater in the cave reflected the varying effects of precipitation, and the δC-13(DIC) was more sensitive to changes in recharge from extreme precipitation and drought events, making it a reliable indicator of hydrological signals in the southwest monsoon region.